[time-nuts] how to feed multiple GPS receivers ?

[Bob kb8tq]

Hi

The “antenna in a window” approach does indeed work. I’m running one right now as 
a matter of fact. I also have other antennas outdoors to compare it to. Even though 
they are not ideally located, they are a lot better than the window mount. Some sort 
of outdoor mount, even if it’s not at the top of the roof should be a pretty high priority. 
In any case, view to the south (in the northern hemisphere / for GPS) is key. 

======

These are reasonable splitters:

https://www.ebay.com/itm/Mini-Circuits-ZB8PD-2-Power-Splitter-Attenuator/121938456381?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 <https://www.ebay.com/itm/Mini-Circuits-ZB8PD-2-Power-Splitter-Attenuator/121938456381?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649>

There are a lot of similar models out there. The main criteria is “cheap” when I go
shopping for them. $20 to $30 for eight ports isn’t to bad. No need to make anything
from scratch. The connectors alone could cost more than the entire splitter ….

=======

There’s no need for this to cost a ton of money or to get overly fancy about it. Outdoors 
is good. A lightning arrestor (and grounding) comes along with that. Timing wise, you 
can get a lot of antenna for not a lot of money. Hitting 4mm x 8 mm 95% error ellipses
is not at all required.(but it can be fun ….). 

Bob

> On Mar 12, 2019, at 3:37 PM, shouldbe q931 <shouldbeq931 at gmail.com> wrote:
> 
> Hi Bob,  and others that responded off list.
> 
> On Mon, Feb 25, 2019 at 2:15 PM Bob kb8tq <kb8tq at n1k.org> wrote:
>> 
>> Hi
>> 
>> On a GPS distribution system the issue of 75 vs 50 ohm cable is pretty
> much a
>> non-issue. A lot of people have run 75 ohms (like Trimble on the TBolt)
> and had
>> no problems from this.
> 
> This is what I thought, thanks for the confirmation.
> 
>> The “TV” splitters are generally spec’d to 2 GHz, so well beyond GPS
> frequencies.
>> Again, it should not be an issue. There are also cheap multi-port
> splitters on the
>> auction sites.
> 
> Some hints on what to search for would be appreciated.
> 
>> DC blocks *are* a good idea. DC loads may or may not be needed. It’s a
> try it and see
>> sort of thing. Some have been known to simply drop a 50 ohm load on one
> port of a
>> 8 way splitter and let that be the DC load. You *can* run into issues
> doing this ….
>> (one device feeds 12V and another is a 3.3V feed …. smoke results …).
> Cable TV
>> DC blocks are dirt cheap ….
> 
> Some DC blocks have been ordered.
> 
>> Ideally you want the antenna as high as you can get it. In an urban area
> with various
>> constraints, that may or may not be very high. Coax losses plus splitter
> losses should
>> be considered when designing something like this. An amplifier ahead of
> the splitter
>> is not at all unusual.
> 
> To begin with I'm just going to use one of the "puck" antennas in the
> window that it is currently in, at which point I'm expecting to discover
> that the loss through the TV splitter means that more gain will be
> required, or a lower loss splitter.
> 
>> With the arrival of world of low cost multi-band GPS devices … put up a
> multi-band
>> antenna. At the very least L1 / L2 (including Glonass coverage). Ideally
> L1 / L2 / L5.
>> Much easier to do it right the first time.
> 
> The longer term plan is to get a L1/L2 (and possibly L5) antenna and roof
> mount it, but stage one is just to get the same feed to the different
> receivers.
> 
>> Bob
> 
> While I'm moderately good at fitting most connectors onto cables, making a
> wilkinson splitter PCB or managing to cut coax to exactly the right length
> do make on out of co-ax its a little bit beyond what I can get away with in
> the workshop kitchen.
> 
> Cheers
> 
> Arne
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.